(function() {
    var lastTime = 0
    var vendors = ['webkit', 'moz']
    
    for (var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
        window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame']
        window.cancelAnimationFrame = window[vendors[x] + 'CancelAnimationFrame'] ||
            window[vendors[x] + 'CancelRequestAnimationFrame']
    }

    if (!window.requestAnimationFrame) {
        window.requestAnimationFrame = function (callback) {
            var currTime = new Date().getTime()
            var timeToCall = Math.max(0, 16 - (currTime - lastTime))
            var id = window.setTimeout(function () {
                callback(currTime + timeToCall)
            },
            timeToCall)
            lastTime = currTime + timeToCall
            return id
        }
    }

    if (!window.cancelAnimationFrame) {
        window.cancelAnimationFrame = function(id) {
            clearTimeout(id)
        }
    }
}())